Washington DC - President Donald Trump on Wednesday told Iran to "get smart soon" and capitulate to his demands amid a destructive war stretching into its third month.

Pentagon chief Pete Hegseth is due to testify before Congress later in the day, but US press reports suggested Trump has already decided to reject Iran's latest proposed deal to reopen the Strait of Hormuz.

According to the Wall Street Journal, he intends to pursue the blockade of Iranian ports until Tehran is forced to dismantle its nuclear program.

"Iran can't get their act together... They better get smart soon," Trump posted on his social media platform, above a mocked-up picture of himself toting a rifle in front of explosions wrecking a desert fortress and the slogan: "No more Mr. Nice Guy."

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Iran has blockaded the strait – a vital conduit for oil and gas shipments from the Gulf – since the US and Israel launched the war two months ago, sending shockwaves through the global economy.

During a White House state dinner Tuesday, Trump falsely told Britain's King Charles III and other guests that Iran has been "militarily defeated", and added: "Charles agrees with me even more than I do – we're never going to let that opponent have a nuclear weapon."

But an Iranian army spokesperson told state TV on Tuesday that "we do not consider the war to be over," saying Tehran had "no trust in America".

"We have many cards that we have not yet used... new tools and methods of fighting based on the experiences of the past two wars, which will definitely allow us to respond to the enemy more decisively" should the fighting resume, Amir Akraminia said in an interview.